Brightening agent for electroplating



United States Patent BRIGHTENING AGENT FOR ELECTROPLATING Richard 8. Robinson, Belmont, Mass., assignor, by mesne assignments, to John A. Manning Paper Company, Inc., Troy, N.Y., a corporation of New York No Drawing. Application July 21, 1958 Serial No. 750,047

6 Claims. (Cl. 204-49) This invention relates to methods and means for the electrodeposition of metals and more specifically to the process of electrodeposition employing a novel type of brightening agent.

Electroplating of metals is a widely used technique,

one of the most important applications of this technique being the electrodeposition of a thin, but bright, coating of nickel on metal parts prior to a final coating of chromium. Moreover, many other important metals such as silver, copper, and cadmium are deposited by electrolytic processes.

It is highly desirable in electroplating to be able to deposit a bright metallic surface which does not subsequently have to be buffed or polished. Any additional steps of buffing or polishing add to the cost of the plating, in terms of additional laborrequirements and the necessity of forming thicker coats. Furthermore, surfaces which can be formed in an extremely bright condition without bufiing are desirable for special applications. One such example is the formation of low-emissivity sur-' faces such as those required for the inner walls of a vacuum insulation device (see for example U.S.P. 2,776,069). This patent discloses that non-buifed, bright surfaces achieve unexpectedly low emissivities.

- Many brighteners are known which can be added to electroplating baths, but many of these have one or more drawbacks. For example, the use of carbon disulfide as a brightening agent in a standard silver-plating bath gives unreliable results; while brightening agents used in nickel-plating sometimes result in the formation of pits and in a material decrease in the ductility of the metal article which has been plated.

From this brief review it will be seen that it is highly desirable to have an electroplating brightening agent which is reliable, easy to mix in and handle, and which is, at the same time, capable of forming a bright metal surface without pitting and without detracting from the ductility of the coated metal. Furthermore, it is desirable to be able to deposit a metal coating which does not have to be bufied, thus making the coating more economical and in some instances imparting novel physical characteristics to the surfaces.

It is therefore an object of this invention to provide a brightening agent which may be added in relatively small quantities to an electroplating bath, and which is at the same time reliable in its performance, thus permitting unskilled workers to use it. It is another object of this invention to provide such a brightening agent which will permit a thin metal coating to be deposited on a surface, a coating which does not have to be further bufied or polished. It is another object to provide a brightening agent, which enhances the formation of a bright, smooth metal surface, and which does not detract from the ductility of the article. These and other objects will become apparent in the following discussion.

The brightening agent of this invention which has been found to achieve the above listed objects is a dry material prepared by dehydrating the mucilage-producing content 2,932,610 Patented Apr. 12, 19.60

of okra pods. The dried, dehydrated okra pod extract (hereinafter referred to as dried okra product) which is suitable for the practice of this invention is a dry powder extracted from okra podsby any suitable process which permits removal of the water, subsequent drying and isolation of the mucilage-producing material contained in the pods. The dried okra product is preferably prepared by a process which reduces the alcohol-soluble materials content to less than 0.8% based on the total weight of the dried okra product, and which as a final step gives a material, preferably at least 60% of the individual particles of which are in a size range from 45 to microns.

One such process comprises dehydrating and precipitating the mueilage-producing material of okra pods by means of an organic dehydrating agent such as one of the lower alcohols, and drying the resulting dehydrated and precipitated materialunder conditions which will not degrade. the final dried okra product.

Another process by which dried, dehydrated okra pod extract may be prepared achieves the extraction of the mucilage-producing material of the okra pod by a form of steam distillation using a Water-immiscible hydrocarbon.

In any process employed to produce the dried okra product required in the process of this invention, it is preferable that the temperatures and times of processing are such as not to render the final product unstable or degraded with respect to its mucilage-producing abilities. Although the reasons why dried okra product is or is not stable are not understood, it appears that the enzymatic activity associated with the naturally occurring pods must be substantially and rapidly arrested to prevent subsequent degradation of the final product.

Although it is not known Why this dried okra product exhibits this novel and unexpected elfect when incorporated into electroplating baths, it may be postulated that this additive serves to alter the crystallization pattern of the metal as it is deposited from. the electroplating bath.

The use of the dried okra product may be further described in the following examples which are meant to be illustrative but not limiting.

In all of the examples given below the dried okra product was evaluated as a brightener by the Hull cell method, under the conditions indicated in each of the examples. The electroplating baths used are those common in the metal deposition art and were prepared according to instructions given in the Metal Finishing Guidebook (1956 Edition). Each bath was filtered and the pH was adjusted according to recommended electroplating procedures.

Mechanical agitation was used to dissolve the dried okra product in the various baths. The solutions which resulted were somewhat gelatinous in nature. The dried okra product is particularly well suited in acid baths inasmuch as it goes into solution very readily in such baths. Any insoluble sediment remaining in each of the baths after the addition of the dried okra product was decanted prior to introduction into the Hull cell. Comparisons of brightness of the resulting deposits were made against a control containing no dried okra product.

Example 1 Silver was plated out from a standard silver cyanide plating solution made up as follows under the conditions indicated:

Current "amps" 1 2,982,610 y r t Plating time min Anode Silver Cathode Copper Temperature F 75 Copper Was plated out from a standard acid bath of the following composition under the conditions indicated:

I Brightening occurred from 10 to 120 amps/ft. com- Copper sulfate g./liter 210 Sulfuric acid 52.5 Dried okra product g -1 Current mps 2 Time ..min 5 Anode Copper Cathode Copper Temperature F .75

The dried okra product resulted in brightening up to 15 amps/ft. when compared with a control bath having no dried okra product.

Example III Cadmium was plated out from the standard electroplating bath given below:

Cadmium oxide g./liter 26.2 Sodium cyanide ..do 128.0 Dried okra product g 1 Current amps 3 Time m' Z Anode Cadmium Cathode Steel Temperature F 100 Brightening occurred up to 50 ampsJftFas compared with the corresponding control. 7

Example IV I V Nickel was plated out using a standard Watts nickel bath with dried okra product. The bath composition and the conditions used are given below:

Temperature F-.. 140

pared with the corresponding control.

In all of the above examples the dried okra product was used in a concentration equivalent to 1 gram of dried okraproduct per liter of plating solution. This concentration represents a maximum, and it is possible to use as little as 0.1 gram per liter of plating solution. v

The dried okra product may be added to the plating baths according to this invention as a dry material or dispersed in a small quantity of water.

It will be seen from the above examples that the use of dried okra product has a brightening effect when used in electroplating baths. It is particularly well suited in the plating of nickel, a most important metal for deposition. It is moreover easily handled and gives consistently reliable and reproducible results.

vWhat isclaimed is:

1. An electrodeposition bath comprising a solution containing ions of metal to be deposited by electrolysis and a dried, dehydrated okra pod extract present in a concentration up to about one gram per liter of said solution.

2. Electrodeposition bath in'accordance with claim 1, wherein said dried, dehydrated okra pod extract is present in concentrations from about 0.1 to about one gram per liter of said solution.

3. An electrodeposition bath comprising a solution containing ions of nickel to be deposited by electrolysis and a dried, dehydrated okra pod extract present in a concentration ranging from about 0.1 to about one gram per liter of said solution.

4. A process of electrodeposition, comprising electrolyzing a solution containing ions of a metal to be deposited by electrolysis and a dried, dehydrated okra pod extract present in a concentration up to about one gram per liter of said solution.

5. A process of electrodeposition of nickel, comprising electrolyzing a solution containing nickel ions and a dried, dehydrated okra pod extract present in a concentration ranging from about 0.1 to about one gram per liter of said solution.

6. A process of electrodeposition in which a solution is electrolyzed, said solution containing ions of metal References Cited in the file of this patent Metal Finishing, June 1940, page 317. 

1. AN ELECTRODEPOSITION BATH COMPRISING A SOLUTION CONTAINING IONS OF METAL TO BE DEPOSITED BY ELECTROLYSIS AND A DRIED, DEHYDRATED OKRA POD EXTRACT PRESENT IN A CONCENTRATION UP TO ABOUT ONE GRAM PER LITER OF SAID SOLUTION. 